The present invention relates to a grinding or separating tool and a method of producing the same.
More particularly, it relates to a grinding or separating tool which has a fiber-reinforced base body with a synthetic plastic matrix, and a working coating of hard material such as diamond grains or boron nitride grains held in a binder.
Grinding tools and separating tools such as saws generally have a working coating composed of active hard material and a base body on which the working coating is mounted. In addition to the hard materials, the working coating also includes a binder for the hard materials. The binder can be a metal, a synthetic resin or ceramic. In certain cases the working coating also has various fillers, depending on the application of the diamond tools.
The base body which has no hard materials but instead performs only the functions of a support for the hard material working coating usually is composed of metal, such as for example aluminum or steel, or of synthetic plastic resin such as for example phenol resin, epoxy resin or polyamide resin. It is known also to provide the synthetic resin with admixtures such as for example metal powder, graphite powder, or fiber structures such as carbon fibers or glass fibers.
Both the working coating and the base body must satisfy very high requirements with respect to the strength, the temperature resistance, the hydraulic resistance and the chemical resistance. Moreover, they must satisfy the requirements of the heat conductivity and the vibration damping. These requirements can be partially satisfied by the use of temperature resistant duroplastic synthetic plastic resins with admixtures of metal powders or graphite.
In earlier time there was a tendency of increasing the cutting speed or the peripheral speed, especially of peripheral grinding discs and saws. The development of high speed grinding and separating tools led as a rule to greater diameters of the discs, since otherwise with conventional machines very high peripheral speeds of more than 250 m/s could not be achieved without problems. On the other hand, high peripheral speeds can be obtained only when the base body has high E-modulus (elasticity modulus) with low density so that the tool does not substantially expand or spring, but instead can take into consideration relatively low loads and expansions. The earlier developments therefore led to utilization of fiber reinforced-composite materials which have a high strength with low weight. This is true especially for the use of carbon fiber-reinforced synthetic resin compound materials which are generally identified as CFK.
In such fiber-reinforced base bodies of synthetic plastic material for high speed tools there is however a problem related to the connection of the base body with the working coating. It is known to connect the working coating with the base body by adhesives. However, this method can result in strength which in many cases does not satisfy the requirements of the high speed grinding. It has been found that the working coatings can be anchored mechanically in the base body or laminated in the base body with a web. Such solutions are however expensive and lead to an increase of the mass of the tool and in some cases to non-uniform mass distribution, so that an additional equalization must be provided.